A wide range of chemicals and dyes are being used in textile industry, and are often found in the wastewater produced. This study attempts to investigate the reduction of COD, TSS, and dye in effluents from the dyeing and washing unit of textile industry, using electrocoagulation process. The reactor is equipped with 10 iron electrodes, connected to a direct current (DC) source in a monopolar electrode configuration. In each stage of the experiment, 2.5 l of the effluent enters the reactor and the effects of a number of important operational parameters such as voltage, pH, and reaction time is studied on the removal of COD, TSS, and dye parameters. Results show that the optimum operational conditions are reaction time of 120 min, voltage of 30 V, and pH of 7, which reduces COD, TSS, and dye by 87%, 91%, and 98%, respectively. Therefore, it has been concluded that the efficiency of pollutants removal from the wastewater improves as voltage and reaction time are increased.

Water scarcity, its necessity in food production, and environmental protection in the world have forced human beings to seek new water sources. Nowadays, application of unconventional water resources (wastewater) has been proposed in countries facing the crisis of water resources shortage; however, a few studies have dealt with this issue. The present study has evaluated the changes in the elements of the soil, irrigated with wastewater. For so doing, an experiment has been conducted on a randomized complete block design with three replications. Soil samples have been collected from the studied regions at two depths of 0-30 cm and 30-60 cm and the studied parameters have included sodium, total calcium, magnesium, some acidity, and electrical conductivity of the soil. Three regions of study (namely no irrigation, irrigation with treated wastewater, and irrigation with river waters) have been taken into consideration. Results have shown increased calcium, magnesium, and pH of the effluent from Zabol Wastewater Treatment Plant compared to the control; however, electrical conductivity and chloride have decreased in wastewater-irrigated soil. The electrical conductivity in the surface layer of wastewater samples, treated with an amount of 2.25 (ds/m), has had the most significant difference to the control and other treatments. It can be concluded that wastewater increases some soil properties, contributing to its restoration.

Urban greenspaces provide ecosystem services like more natural ecosystems do. For instance, vegetation modifies soil properties, including pH and soil organic matter content, yet little is known about its effect on metals. We investigated whether the accumulation and mobility of heavy metals, nutrients and carbon is affected by plant functional types (evergreen or deciduous trees, lawns) in urban parks of varying ages in southern Finland. Plant types modified soil physico-chemical parameters differently, resulting in diverging accumulation and mobility of metals and other elements in park soils. However, the effects of plant functional type depended on park age: lawns in parks of ca. 50 y old had the highest contents of Cr, Cu, Fe, Mn, Ni, and Zn, and in these, and older parks (>100 y old), contents of most metals were lowest under evergreen trees. The mobility of metals and other elements was influenced by the amount of water leached through the soils, highlighting the importance of vegetation on hydrology. Soils under evergreen trees in young parks and lawns in intermediately-aged parks were most permeable to water, and thus had high loads of Ca, Cr, Cu, Fe, Ni, tot-P and tot-N. The loads/concentrations of elements in the leachates was not clearly reflected by their content/concentration in the soil, alluding to the storage capacity of these elements in urban park soils. Our results suggest that in urban systems with a high proportion of impermeable surfaces, park soil has the potential to store nutrients and metals and provide an important ecosystem service particularly in polluted cities.

Microplastic (MP) vector effects have been well described in the literature but surprisingly little is in known about the impact of MPs on the intestinal uptake of contaminants. The present study aimed to determine whether the intestinal fate of Ag was affected by the presence of polyethylene MP beads. Ag (added as ¹¹⁰ᵐAg) was introduced into the lumen of rainbow trout (Oncorhynchus mykiss) anterior/mid-intestine gut sac preparations as Ag only, Ag and MPs (co-exposure) and Ag-incubated MPs (where Ag was adsorbed to the MP). Results show that after 3 h exposure the distribution of accumulated Ag between the four intestinal compartments (mucus layer, mucosal epithelium, muscle layer and serosal saline) was not affected by either MP condition when compared to Ag alone (p > 0.05, One way ANOVA). Across all treatment groups mucus layer binding dominated (54.2–72.6%) whereas relatively little Ag was transported to the blood compartment (i.e. combined muscle layer and serosal saline compartments, 8.5–15.0%). Accompanying adsorption/desorption studies were performed in relevant media. Over 24 h, 60.6± 2.9% of the available Ag in artificial freshwater adhered to the surface of the PE MPs. In pH adjusted luminal fluids (pH 2.2, 4.1, 7.4 and 9.8) that span the range of conditions encountered within the rainbow trout digestive tract, there was almost complete dissociation at acidic pHs within 3 h (<2% remaining on MPs at both pH 2.2 and pH 4.1). Such pHs are typical of piscine stomach. Based on our finding we suggest that following the ingestion of MPs with adsorbed pollutants, desorption would occur prior to entering the site of uptake. The MPs themselves have no impact on the trans-epithelial transport of the contaminant, but the net result of the MP vector effect is to potentially introduce labile contaminant forms into the intestine.

The anaerobic digestion of food waste for energy recovery produces a nutrient-rich digestate which is a valuable source of crop available nitrogen (N). As with any ‘new’ material being recycled to agricultural land it is important to develop best management practices that maximise crop available N supply, whilst minimising emissions to the environment. In this study, ammonia (NH3) and nitrous oxide (N2O) emissions to air and nitrate (NO3−) leaching losses to water following digestate, compost and livestock manure applications to agricultural land were measured at 3 sites in England and Wales. Ammonia emissions were greater from applications of food-based digestate (c.40% of total N applied) than from livestock slurry (c.30% of total N applied) due to its higher ammonium-N content (mean 5.6 kg/t compared with 1–2 kg/t for slurry) and elevated pH (mean 8.3 compared with 7.7 for slurry). Whilst bandspreading was effective at reducing NH3 emissions from slurry compared with surface broadcasting it was not found to be an effective mitigation option for food-based digestate in this study. The majority of the NH3 losses occurred within 6 h of spreading highlighting the importance of rapid soil incorporation as a method for reducing NH3 emissions. Nitrous oxide losses from food-based digestates were low, with emission factors all less than the IPCC default value of 1% (mean 0.45± 0.15%). Overwinter NO3− leaching losses from food-based digestate were similar to those from pig slurry, but much greater than from pig farmyard manure or compost. Both gaseous N losses and NO3− leaching from green and green/food composts were low, indicating that in these terms compost can be considered as an ‘environmentally benign’ material. These findings have been used in the development of best practice guidelines which provide a framework for the responsible use of digestates and composts in agriculture.

Concern over tetracyclines (TCs) complexation with metals in the environment is growing as a new class of emerging contaminants. TCs exist as a different net charged species depending on their dissociation constants, pH and the surrounding environment. One of the key concerns about TCs is its strong tendency to interact with various metal ions and form metal complexes. Moreover, co-existence of TCs and metals in the environment and their interactions has shown increased antibiotic resistance. Despite extensive research on TCs complexation, investigations on their antibiotic efficiency and pharmacological profile in bacteria have been limited. In addition, the current knowledge on TCs metal complexation, their fate and risk assessment in the environment are inadequate to obtain a clear understanding of their consequences on living systems. This indicates that vital and comprehensive studies on TCs-metal complexation, especially towards growing antibiotic resistance trends are required. This review summarizes the role of TCs metal complexation on the development of antibiotic resistance. Furthermore, impact of metal complexation on degradation, toxicity and the fate of TCs in the environment are discussed and future recommendations have been made.

Bacteria–phyllosilicate complexes are commonly found in natural environments and are capable of immobilizing trace metals. However, the molecular binding mechanisms of heavy metals to these complex aggregates still remain poorly understood. This study investigated Cd adsorption on Gram-positive Bacillus subtilis, Gram-negative Pseudomonas putida and their binary mixtures with montmorillonite using surface complexation model, Cd K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and isothermal titration calorimetry (ITC). We have shown that larger amounts of Cd are adsorbed by B. subtilis than by P. putida at pH<∼6, and Cd sorption that binding to phosphate groups plays a more important role in P. putida than in B. subtilis. This remind us that we should consider the microbe species when predict the biochemical behavior of trace metals in microbe-bearing environments. The observed Cd adsorption on the binary bacteria–clay composites was more than that predicted based on the component additivity approach. When taking bacteria–clay (1:1 mass ratio) as a representative example, an approximately 68%:32% metal distribution between the bacterial and mineral fraction was found. Both the EXAFS and ITC fits showed that the binding stoichiometry for Cd-carboxyl/phosphate was smaller in the binary mixtures than that in pure bacteria. We proposed that the significant deviations were possibly due to the physical-chemical interaction between the composite fractions that might reduce the agglomeration of the clay grains, increase the negative surface charges, and provide additional bridging of metals ions between bacterial cells and clays.

Widely used titanium dioxide (TiO2) nanoparticles are likely to accumulate ultimately in sediments and potentially pose a risk to water ecosystems. This study evaluated the effect of TiO2 nanoparticles on the photodissolution of particulate organic matter (POM) through fluorescence spectroscopy. Excitation-emission matrices and parallel factor analyses revealed that the fluorescent characteristics of produced dissolved organic matter (DOM) during photodissolution of suspended sediment and synthetic particulate organic matter (SPOM) were primarily humic-like. SPOM particles appeared to simulate well the photodissolution of suspended sediment. Quasi-complete increases in fluorescence intensity and chromophoric DOM (CDOM) abundance were reached after 90, 60, and 50 min irradiation for TiO2 concentrations of 0, 2, and 5 mg L−1, respectively. The faster increment of fluorescence intensity and CDOM abundance indicated the photocatalytic dissolution of SPOM, as opposite charges between TiO2 and SPOM at pH = 4 favored the adsorption of TiO2 onto SPOM. For sediments, the CDOM abundance and fluorescence intensity decreased with increasing TiO2 concentration, resulting from the photocatalytic degradation of photoproduced DOM from sediments. These results demonstrated that pH plays an important role in the photocatalytic dissolution of POM by TiO2. Therefore, appropriate pH controls should be implemented when TiO2 are used to treat sediments contaminated with organic pollutants. Finally, with increasing use of TiO2, its accumulation in sediments may affect the fate of carbon, nutrients, and heavy metals in shallow-water ecosystems.

Carbazole in source water is a potential precursor for toxic chlorocarbazoles in drinking water when chlorine is used as a disinfection agent in drinking water treatment plants. However, the reactivity of carbazole and the specific structures and predominant analogues of chlorocarbazoles produced during aqueous chlorination remain unknown. In this study, the aqueous chlorination of carbazole was performed to characterize its reactivity and the chlorinated products. Chlorocarbazoles generated from carbazole were identified by a comprehensive two-dimensional gas chromatography-mass spectrometry method, and their molecular structures were predicted by the Fukui index of electrophilic attack, f−1(r). As a result, the comprehensive chlorination pathway of carbazole was extrapolated with a total of nine chlorocarbazoles identified, including two monochlorocarbazoles (3-chlorocarbazole and 1-chlorocarbazole), four dichlorocarbazoles (3,6-dichlorocarbazole, 1,6-dichlorocarbazole, 1,3-dichlorocarbazole and 1,8-dichlorocarbazole), two trichlorocarbazoles (1,3,6-trichlorocarbazole and 1,3,8-trichlorocarbazole) and one tetrachlorocarbazole (1,3,6,8-tetrachlorocarbazole). The f−1(r) value indicates that the C1, C3, C6 and C8 atoms of carbazole were the favored positions for electrophilic attack, with the C3 and C6 atoms being the predominant sites for chlorine substitution. 3-Chlorocarbazole, 3,6-dichlorocarbazole, 1,3,6-trichlorocarbazole and 1,3,6,8-tetrachlorocarbazole were the major analogues of each chlorocarbazole group; however, the production of minor analogues such as 1-chlorocarbazole and 1,6-dichlorocarbazole should not be overlooked. The chlorination of carbazole was a pseudo first order reaction with a reaction rate of 0.1836 nmol/(L· h) and half-life of 3.77 h (pH = 6.4, Cl2 = 4.7 mg/L), and the chlorination rate of carbazole was approximately 5 times faster than that of an known chlorination precursor pyrene. These results showed that Fukui index was efficacious to predict the chlorination sites of aromatic compounds, and that carbazole is readily transformed into toxic chlorocarbazoles in drinking water treatment plants that use chlorine as a disinfection agent.

The novel eco-friendly algaecidal naphthoquinone derivate was used to control harmful algal bloom causing species Stephanodiscus and, its effect was assessed on other undesired and non-targeted microbial communities. We conducted a mesocosm experiment to investigate the effects of this novel algaecide on native microbial communities rearing in water collected from Nakdonggang River. Upon treatment of the mesocosm with the naphthoquinone derivate the concentration of Chl-a decreased from 20.4 μg L−1 to 9.5 μg L−1 after 2 days. The turbidity has also shown decrement (exhibited 15.5 NTU on the 7th day). The concentrations of DOC and phosphate in the treatment were slightly higher than those in the control due to the decomposition of dead Stephanodiscus, whereas the DO and pH in the treated condition were slightly lower than those in the control; which was due to increment of organic acids and higher degradation activity. Results showed that bacterial abundance were not significantly different but community composition were slightly different as revealed by NGS (Next generation sequencing). The variation in HNF (Heterotrophic nanoflagellates) revealed that the bacterial community composition changed following the change in bacterial abundance. During the treatment, the abundance of Stephanodiscus was significantly reduced by more than 80% after 6 days, and the abundance of ciliates and the dominant species, Halteria grandinella, had shown marked decline. The abundance of zooplankton sharply decreased to 5 ind. L−1on the 8th day but increased again by the end of the study period. The Shannon-Wiener diversity index of phytoplankton, ciliates and zooplankton in the treated mesocosm increased significantly after 4, 7 and 8 days, respectively. The marked changes in the ecosystem structure were observed in treatment compare to control. However, the beneficial microalgal populations were not affected which indicated possibility of restoration of treated ecosystem and regain of healthy community structure after certain period.